1. Field of the Invention
The present invention relates to an RFID (Radio Frequency Identification) tag. The “RFID tag” used in the present specification is also called an “Inlay for RFID tag” because it is also used as an internal structural member (inlay) for an “RFID tag”. Otherwise, the “RFID tag” is also called a “radio IC tag”. Moreover, this “RFID tag” includes a non-contact type IC card.
2. Description of the Related Art
In recent years, an external device represented by a reader/writer and various RFID tags for exchanging information using radio waves on a non-contact basis have been proposed. As a kind of such RFID tags, a tag having a structure such that an antenna pattern for radio wave communication and an IC chip are mounted on a base sheet formed of plastic or paper has also been proposed. The RFID tag of the type explained above is considered to be used in such a mode that such a tag is attached to items and these items can be identified through an exchange of information of such items using an external device.
In such an application mode of the RFID tag, illegal use to obtain, for example, an expensive item as a low price item by peeling the RFID tag attached to a certain item, then attaching this RFID to the other item to control the external device to erroneously recognize the relevant item may be assumed. Therefore, a technique to avoid such illegal use has been requested.
Under such a present situation, a technique for disabling communication by generating breakdown of the antenna pattern at the time of peeling the RFID tag has also been proposed (for example, patent documents 1 to 8).
FIG. 1 is a front elevation (A) and a side elevation (B) illustrating the condition before peeling of the RFID tag based on the related art.
The RFID tag 1 illustrated in FIG. 1 is formed of an antenna pattern provided on a base sheet 13, an IC chip 11 connected to the antenna pattern 12 with a bump 16, and a cover sheet 14 bonded to the base sheet 13 with a bonding agent 15 covering the antenna pattern 12 and IC chip 11.
This RFID tag 1 is used through bonding to an item in the side of the base sheet 13. A bonding force of the bonding agent 15 is set weaker than that when the side of base sheet 13 is bonded to an item. Therefore, if the RFID tag 1 is peeled by an illegal user who is trying to conduct illegal use, the cover sheet 14 is peeled from the base sheet 13.
Moreover, the antenna pattern 12 is provided to and fro with regions, which are rather weak in bonding with the base sheet 13.
FIG. 2 is a front elevation (A) and a side elevation (B) of the condition after peeling of the RFID tag in the related art.
When the cover sheet 14 illustrated in FIG. 1 is peeled from the base sheet 13, the antenna pattern 12 is peeled together with the cover sheet 14 at the areas 12a where the bonding with the base sheet 13 is weak. Accordingly, the antenna pattern 12 loses its function as a communication antenna, disabling communication.
As a technique for avoiding illegal use, a technique has been proposed, in which an exclusive pattern broken at the time of peeling is provided to the RFID tag in addition to the antenna pattern and a breakdown of the exclusive pattern is detected with an IC chip.
FIG. 3 is a condition (A) before peeling and a condition after peeling of the other RFID tag in the related art.
The RFID tag 2 illustrated in FIG. 3 is provided with an antenna pattern 22, an IC chip 21 connected to the antenna pattern 22, and a pattern 23 for breakdown which is made conductive with a conductive ink 24. Moreover, although not illustrated, a base sheet and a cover sheet are also provided like the RFID tag illustrated in FIG. 1.
In the case of this RFID tag 2, the cover sheet is peeled from the base sheet when an illegal user who is trying to conduct illegal use peels the RFID tag 2. In the case of this RFID tag 2, the conductive ink 24 splashes for setting the pattern 23 for breakdown to the insulating condition when the cover sheet is peeled. Meanwhile, the IC chip 21 detects such insulating condition of the pattern 23 for breakdown. Moreover, breakdown of the pattern can also confirmed visually with the conductive ink 24 splashed.
In the case of the RFID tag 2 illustrated in FIG. 3, the antenna pattern 22 and communication function are maintained even after the cover sheet is peeled and peeling of the RFID tag 2 is notified to an external device at the time of communication with the external device.
Examples of such technology may be found in patent documents such as U.S. Patent Application Publication No. 2003/075608, U.S. Pat. No. 6,421,013, U.S. Patent Application Publication No. 2003-524811, Japanese Patent Document JP-A No. 2003-173477, Japanese Patent Document JP-A No. 2005-31153, U.S. Patent Application Publication No. 2003-517659, Japanese Patent Document JP-A No. 2003-346121, Japanese Patent Document JP-A No. 2002-362613, and Japanese Patent Document JP-A No. 2002-150248.
However, the related art, as explained above has a problem in that since a part of the tag is broken when the RFID is peeled and the broken area is apparent, a motive or a chance to repair the broken area will be given to a person who is trying to illegally use the tag and thereby the effect for eliminating illegal use becomes insufficient. Moreover, in the related art, a reader such as the reader/writer is controlled to erroneously recognize the item information when the RFID tag attached to a certain item is peeled and then attached again to the other item.
For example, an illegal use may be assumed here. Namely, the RFID tag to which low price item information is written is once peeled from the item and is then attached again to an expensive item for giving a false price. Therefore, the technique for avoiding such illegal use has been expected.